This article discusses an experiment to determine the accuracy, reproducibility, and repeatability of forensic footwear examiners’ decisions for a selection of footwear impressions that were chosen because they were broadly representative of those encountered in typical casework.
The interpretation of footwear evidence relies on the expertise of forensic footwear examiners. Here, the authors report on the largest study to-date of the accuracy, reproducibility (inter-examiner variation), and repeatability (intra-examiner variation) of footwear examiners’ decisions. In this study, 84 practicing footwear examiners each conducted up to 100 comparisons between questioned footwear impressions (provided as photographs and digital images) and known footwear (provided as photographs, transparent test impressions, and digital images), resulting in a total of 6610 comparisons. The quality and characteristics of the impressions were selected to be broadly representative of those encountered in casework. A multilevel conclusion scale was used: 40 percent of responses were definitive conclusions (identification or exclusion); 14 percent probable conclusions (high degree of association or indications of non-association); 40 percent were class associations (association of class characteristics or limited association of class characteristics); and six percent were neutral conclusions (inconclusive or not suitable). The authors also discuss non-mated comparisons, erroneous identifications, and erroneous exclusions. Examiners’ assessments of whether a questioned impression was suitable for comparison were notably inconsistent and may benefit from standardization. The authors conclude that rates of correct definitive conclusions are directly associated with the quality of the questioned impression and the extent of class similarities/differences between the questioned impression and known footwear. Publisher Abstract Provided